Ignition system



Feb. 6, 1962 o. M. KURITZA 3,019,782

IGNITION SYSTEM Filed July 1, 1958 INVENTOR. Oleh M. Kurifza llnited rates This invention relates generally to ignition systems for initiating combustion and more particularly to such ignition systems utilizing a transistor power oscillator operating from a low voltage electrical system for use with an internal combustion engine or with a gasoline heater.

Internal combustion engines such as used in presentday automobiles utilize a coil and a timer with contact points which make and break a circuit from the battery to the coil so that pulses are developed in the coil. The secondary circuit of the coil is connected through a distributor to the spark plugs of the cylinders of the engine so that the pulses are selectively applied to ignite charges in the various cylinders. In order to provide the high voltage required, the current in the battery circuit is quite heavy so that arcing takes place at the contacts which make and break this circuit and this causes the contacts to corrode and become pitted with resultant poor timing accuracy and short contact life.

It is, therefore, desired to provide an ignition system wherein the current which passes through the timer points is reduced so that the points will have longer effective life. Vacuum tube circuits have been proposed but these require a higher operating voltage than that which is available with most internal combustion engines, and the complete circuit including the power supply is too expensive to be practical. l-hirther, the vacuum tubes used in such systems are subject to failure so that the life expectancy is not materially increased. It has also ben proposed to use a transistor as a switch in ignition systems and this makes it possible to reduce the current through the contact points, but it has been ditlicult to provide rapid rise and decay of the current through the transistor to produce the sharp voltage pulse required.

It is, therefore, an object of the present invention to provide an improved ignition system for initiating combustion which will operate for long periods without maintenance of any kind.

Another object of the invention is to provide an ignition system for an internal combustion engine wherein the firing pulses are controlled by contact points through which very small current flows.

A further object of the invention is to provide an ignition system for an internal combustion engine wherein a steadily increasing voltage is applied for each firing to provide complete firing action with a minimum voltage.

A feature of the invention is the provision of an ignition system including a transistor oscillator operating from a low voltage such as the battery of an automobile and which provides the ignition voltage for an internal combustion engine or for a gasoline heater.

A further feature of the invention is the provision of an ignition system for an internal combustion engine including a transistor oscillator which is selectively rendered operative to apply oscillations to ignition means of the engine cylinder in response to operation of the timer thereof.

Another feature is the provision of a transistor oscillator having a transformer providing feedback and for producing high voltage oscillations, with the timer points of the engine being connected in the oscillator circuit to selectively render the oscillator operative.

Still another feature of the invention is the provision of a transistor oscillator ignition system for an internal combustion engine wherein the frequency of the oscillator EfilQ/ZSZ Patented Feb. 6, 1962 is substantially greater than the frequency of operation of the contact points even at maximum engine speed, so that a plurality of cycles of oscillation is applied at each firing. The oscillations do not have the high current transients produced by standard systems which cause vaporization at the spark plug gap and, therefore, spark plugs used with the new ignition system will have increased life.

The invention is illustrated in the accompanying drawing in which:

FlG. 1 illustrates the ignition system in accordance with the invention utilized in an automobile engine;

FIGS. 2 and 3 show modified oscillators for use in the system of FIG. 1; and

FIG. 4 illustrates an ignition system for use with a gasoline heater.

5 The ignition system in accordance with the invention includes a transistor oscillator having a transformer with a saturable core and a plurality of windings thereon. Feedback for sustaining oscillations is obtained through windings of the transformer. Operating voltage is applied to the transistor electrodes from the vehicle electrical system which may include a l2-volt battery. The ignition system may be used to provide ignition voltage for an internal combustion engine or for a gasoline heater. When used in an engine, the contact points associated with the timing mechanism of the engine are connected to the oscillator circuit and are effective when closed to short a portion of the circuit and thereby prevent feedback so that oscillations fail. Accordingly, when the points open, feedback is provided so that oscillations start immediately. Alternatively, the contact points may be connected to close a normally open circuit to provide oscillations at the desired time. The oscillator circuit is designed so that the frequency of oscillations is several times the highest frequency of occurrence of the firing pulses so that at each firing a plurality of cycles of oscillations will be applied. The transformer has an output winding coupled to the distributor through which the oscillations are applied to the spark plugs of the individual cylinders. In each cycle the voltage builds up in a smooth wave to improve the spark formation at the spark plugs. Inasmuch as the battery voltage drops substantially during starting because of the load of the starter motor, the oscillator must be designed to operate at a voltage less than the nominal battery voltage. A resistor may be connected to drop the battery voltage after the engine has started.

Referring now to the drawings, an internal combustion engine to is shown in FIG. 1 having a plurality of spark plugs .11 associated with the individual cylinders. The spark plugs are connected to a distributor 12 which selectively applies firing signals thereto. A timer 13 includes contact points 14 and 15 which are selectively opened and closed by action of the timer. The timer 13 and distributor 12 are mechanically connected to the engine and are operated in synchronism therewith. The parts of the engine described above are all standard components .of internal combustion engines.

The ignition system for the engine includes an oscillator provided by the transistor 20' and transformer 21. The transistor 26 has a base electrode 22, a collector electrode 23, and an emitter electrode 24. The transformer is shown including a primary winding 25, a feedback winding 26, and an output winding 27. The transistor is energized from battery 30 through the voltage divider electrode of the transistor and is connected to the primary winding 25 of the transformer. Signals in the winding 25 are inductively coupled to the feedback winding 26 for application to the base electrode 22. This feedback from the collector electrode through winding 25 to winding 26 and then to the base electrode causes oscillations to occur, which are applied from the output winding 27 to the distributor 12. The core of the transformer 21 may be saturated so that sharp pulses are produced in the output winding. The contact points 14 and 15 are connected to the opposite ends of the feedback winding 26.

It will be apparent from a consideration of the circuit that when contacts 14 and 15 close, a short circuit is placed across feedback windings as so that no feedback can be applied therethrough to the base electrode 22 of the transistor. Accordingly, the oscillations will stop. As soon as the timer 13 operates to open contacts is and 15, oscillations will start and the pulsed oscillations will be applied to the distributor 12. The timer 13 can be set so that the first pulse from the oscillator will be applied through the distributor to a spark plug at the desired timed relation with respect to movement of the piston in the cylinder fired by the spark plug. This timing can be controlled in the manner it is now being controlled in internal combustion engines.

It has been found that when the starter switch 35 is operated to connect the starter 36 to the battery 30, the voltage of the battery decreases substantially. The nominal 12-volt battery as commonly used may provide a voltage of only 8 /2 volts when the starting motor is connected to the battery through the contacts 37. Accordingly, the oscillator must be designed to provide ignition voltage adequate for starting the engine when the battery has this low voltage. In order to reduce the voltage from the battery applied to the oscillator after the engine has started, a resistor 31 may be provided in the energizing circuit. This resistor is bridged by contacts 38 on the starter switch 35 so that during starting action, the contacts 38 are closed to provide a short circuit about resistor 31 and the full battery voltage is applied to the transistor oscillator. When the engine is started and the switch 35 is released, the resistor 31 is connected in the circuit to drop the voltage from the battery. The value of resistor 31 can be selected to compensate for the battery voltage drop which takes place in a particular engine system.

In FIG. 2 there is shown a modified oscillator circuit which may be used in the system of FIG. 1. The transistor 40 is of the NPN type and is particularly suitable for use in a vehicle in which the positive terminal of the battery is grounded. The bias circuit for the transistor may be identical to that shown in FIG. 1 with the constants being selected to provide the required voltages for a particular transistor. In the system of FIG. 2, the contact points 14 and 15 controlled by the engine timer are connected across the primary winding 25 of the transformer. Accordingly, when the points are closed, the primary winding 25, which is in the feedback circuit, as stated above, is shorted so that the oscillator stops, and when the points are open, the oscillator starts oscillating. This has the advantage that one of the contacts may be connected to ground.

In FIG. 3 there is shown a still further embodiment of the oscillator. In this circuit, the transistor 45 is of the PNP type and has its collector electrode grounded. The feedback winding of the transformer is connected to the base electrode through the contact points 14 and 15. In this arrangement, the oscillator will operate when the con tacts are closed to complete the circuit, whereas in the prior circuits, the oscillator operates when the points are open to remove a short from a feedback winding. The circuit of FIG. 3 is arranged to operate in a vehicle having the negative voltage of the battery grounded, and operates from a positive potential.

It is obvious that other oscillator circuit arrangements than those shown in FIGS. 1, 2, and 3 may be used. Transistors of various types may be used with feedback between the electrodes being provided in various known Ways. The points of the timer may be connected in the circuit to short a portion of the circuit or to selectively complete the circuit, with the position of the points in the circuit being arranged to provide the best arrangement for a particular application.

In FIG. 4 there is illustrated an ignition system for use with a gasoline heater. The system includes an oscillator generally similar to the oscillator of the system shown in FIG. 1. The oscillator includes a transistor 50 and a saturable core transformer 51. The collector electrode of transistor 50 is connected to the primary winding 52 of transformer 51, and feedback is applied through winding 53 to the base electrode of the transistor. Energizing potential is applied to the transistor from the 12-volt system of the vehicle through switch 55 which applies a positive potential through stabilizing resistor 56 to the emitter electrode of transistor 50 which is of the PNP type. Resistors 57 and 58 form a voltage divider to apply a smaller positive potential through windings 53 to the base electrode. The transformer has a secondary winding 54 which applies a stepped-up voltage to the spark plug or other spark producing element of the heaterproper 59.

The ignition system in accordance with the invention has been found to operate satisfactorily with an internal combustion engine when the oscillator operates at a fre-.

quency of 6 kilocycles. The output voltage of the oscillator as measured across a l megohn resistor was 10 kilovolts. This is considerably less than the voltage normally used in ignition systems, but provides satisfactory operation. It is believed that a lower ignition voltage can be used because the voltage builds up steadily in each cycle instead of being a sudden pulse as in standard systems. This is advantageous in that the life of the spark plugs may be thereby increased.

The system in accordance with the invention has been found to have many important advantages. The current through the breaker points, which are in the feedback circuit of the oscillator, is very small and the breaker points should last for the life of the engine. This is to be contrasted with the life of breaker points in present automobile engines which last 10,000 miles or so. Another advantage is that the voltage of the oscillator ignition system is not reduced at high speed to the same extent as in standard systems. A further advantage is that the current drain on the automobile electrical system may be reduced as compared to standard systems. The current required by the transistor oscillator in accordance with the invention is of the order of .5 amperes while standard systems draw about 2 amperes. The system also has the advantage'that the oscillations produced are of a constant frequency and, because of this, it may be easier to reduce the effect of electrical interference from the ignition system.

I claim:

1. An ignition system for an internal combustion engine having a plurality of cylinders with ignition means, and having a timer having contacts which intermittently open and close to control the firing of the cylinders and a distributor to apply firing signals in turn to the ignition means, said system including the combination with said timer and distributor of an oscillator having a transistor and a transformer, said transformer having first, second, and third inductively coupled winding portions, potential supply means, circuit means coupling said transistor to said potential supply means and to said first and second winding portions to provide feedback therethrough to produce oscillations in said transistor, said circuit means having a portion connected to the timer contacts to selectively control the feedback in said circuit means to render said oscillator operative and inoperative, and means conmeeting said third winding portion to the distributor to apply the oscillations thereto.

2. In an ignition system for an internal combustion engine having a plurality of cylinderswith ignition means, and having a timer to control the firing of the cylinders and a distributor to apply firing signals in turn to the ignition means, the combination including an oscillator having a transistor and a transformer, said transformer having a saturable core with first, second and third inductively coupled windings thereon, potential supply means, circuit means coupling said transistor to said potential supply means and to said first and second windings to provide feedback through said windings to produce oscillations in said transistor, said circuit means having a portion connected to the timer to selectively render said feedback operative and inoperative, said transformer and said circuit means being constructed so that the frequency of oscillations is substantially greater than the frequency of operation of the timer whereby a plurality of oscillations is produced each time the timer renders the feedback operative, and means connecting said third winding to the distributor to apply the oscillations thereto.

3. An oscillator for an ignition system for an automotive vehicle having an internal combustion engine with a plurality of cylinders having ignition means, and with a timer and a distributor to apply firing signals in turn to the ignition means of the cylinders, and which vehicle includes a low voltage electrical system, said oscillator having a transistor, a transformer having a saturable core with first, second, and third inductively coupled windings thereon, and circuit means for coupling said transistor to the vehicle electrical system to provide operating voltage therefor, said circuit means connecting said first and second windings to said transistor to provide feedback through said windings so that oscillations are produced, said circuitmean-s having a portion for connection to the timer to selectively render said feedback operative and inoperative, said transformer and said circuit means being constructed so that the frequency of said oscillation is such that a plurality of oscillations is produced each time the timer renders the feedback operative, said core being saturated whereby the oscillations in said third winding are in the form of sharp pulses, and means for connecting said third winding to the distributor to apply the oscillations thereto.

4. An ignition system for an internal combustion en- 'gine which has a plurality of cylinders with ignition means, a timer with contacts intermittently opened to control the firing of the cylinders and a distributor to apply firing signals in turn to the ignition means, said system including in combination an oscillator having a transistor and a transformer, potential supply means providing energizing potential for said transistor, said transformer having a saturable core with first, second, and third inductively coupled windings thereon, feedback circuit means coupling said transistor to said first and second windings to provide feedback through said windings to produce oscillations therein, said feedback circuit means having a portion connected to the timer contacts to intermittently short a portion of said feedback circuit means and thereby render said oscillator inoperative, said feedback circuit causing operation of said oscillator in response to opening of the timer contacts, said transformer and said feedback circuit means being constructed so that the frequency of said oscillator is substantially greater than the frequency of operation of the timer for all speeds of the engine whereby a plurality of oscillations is produced each time the timer renders the feedback circuit operative, and means connecting said third winding to the distributor to apply the oscillations thereto.

5. An ignition system for an internal combustion engine which has a plurality of cylinders with ignition means, a timer with contacts intermittently opened to control the firing of the cylinders, a distributor to apply firing signals in turn to the ignition means, an electrical starter for the engine, a low voltage direct current electrical system, and a switch for connecting the starter to the electrical system; said system including in combination, an oscillator having a transistor and a transformer, said transformer having a saturable core with first, second, and third inductively coupled windings thereon, means connecting said transistor to the electrical system for providing operating voltages to said transistor therefrom, said last named means including means connected to the starter switch for reducing the voltage applied from the electrical system after the engine is started, feedback circuit means coupling said. transistor to said first and second windings to provide feedback through said windings to produce oscillations in said transistor, said feedback circuit means having a portion connected to the timer contacts to intermittently short a portion of'said feedback circuit means and thereby render said oscillator inoperative, said feedback circuit causing operation of said oscillator in response to opening of the timer contacts, said transformer and said feedback circuit means being constructed so that the frequency of said oscillator is substantially greater than the frequency of operation of the timer whereby a plurality of oscillations is produced each time the timer renders the feedback circuit operative, and means connecting said third winding to the distributor to apply the oscillations thereto.

6. In an automotive vehicle having an internal combustion engine with a plurality of cylinders having ignition means, and with a timer and a distributor to apply firing signals in turn to the ignition means of the cylinders, and which vehicle includes a low Voltage electrical system, an ignition system including an oscillator having a transistor with base, collector, and emitter electrodes, a transformer having a saturable core with first, second, and third inductively coupled windings thereon, circuit means connecting said collector electrode to said first winding and connecting said base electrode to said second winding to provide feedback through said windings so that oscillations are produced, said circuit means connecting said base and emitter electrodes of said transistor to the vehicle electrical system to provide operating voltage therefor, said circuit means having a portion connected to the timer to selectively render said feedback operative and inoperative, said transformer and said circuit means being constructed so that the frequency of said oscillations is such that a plurality of oscillations is produced each time the timer renders the feedback operative, and means connecting said third winding to the distributor to apply the oscillations thereto.

7. In an automotive vehicle having an internal cornbustion engine with a plurality of cylinders having ignition mean-s, and with a timer and a distributor to apply firing signals in turn to the ignition means of the cylinders, and which vehicle includes a low voltage electrical system, an ignition system including an oscillator having a transistor with base, collector, and emitter electrodes, a transformer having a saturable core with first, second, and third inductively coupled windings thereon, circuit means connecting said collector electrode to said first winding, said circuit means connecting said base electrode through said second Winding to the electrical system to provide feedback through said windings so that oscillations are produced, said circuit means connecting said emitter electrode of said transistor to the vehicle electrical system to provide operating voltage therefor, said circuit means having a portion connected to the timer to selectively render said feedback operative and inoperatiove, said transformer and said circuit means being constructed so that the frequency of said oscillations is such that a plurality of oscillations is produced each time the timer renders the feedback operative, said core being saturated whereby the oscillations in said third winding are in the form of sharp pulses, and means connecting said third winding to the distributor to apply the oscillations thereto.

8. An ignition system for an automotive vehicle having an internal combustion engine with a plurality of cylinders having ignition means, a timer with contacts which open to initiate firing signals and a distributor to apply firing signals in turn to the ignition means of the cylinders, and which vehicle includes a low voltage electrical system, said ignition system including the combination with said timer and distributor of an oscillator having a transistor with base, collector, and emitter electrodes, a transformer having a saturable core with first, second and third inductively coupled windings thereon, circuit .means connecting said collector electrode to said first winding and connecting said base electrode to said second winding to provide feedback through said windings so that oscillations are produced, said circuit means connecting said base and emitter electrodes of said transistor to the vehicle electrical system to provide operating voltage therefor, said circuit means having a portion connecting the timer contacts across said second winding to selectively short'said second winding and then remove the short to thereby render said feedback inoperative and operative respectively, said transformer and said circuit means being constructed so that the frequency of said oscillations is such that a plurality of oscillations is produced each time the timer renders the feedback operative, and means connecting said third winding to the distributor to apply the oscillations thereto.

9. An ignition system for an automotive vehicle having an internal combustion engine with a plurality of cylinders having ignition means, a timer with a contact which is connected to a reference potential point and then opened to initiate firing signals and a distributor to apply firing signals in turn to the ignition means of the cylinders, and which vehicle includes a low voltage electrical system, said ignition system including the combination with said timer and distributor of an oscillator having a transistor with base, collector, and emitter electrodes, a transformer having a saturable core with first, second and third windings inductively coupled, thereon, circuit means connecting said first winding between said collector electrode and the reference potential point, said circuit means connecting said base and emitter electrodesof said transistor to the vehicle electrical system to provide operating voltage therefor, with said base electrode being connected to said second winding to provide feedback through said windings so that oscillations are produced, said circuit means connecting said collector electrode to the timer contact to connect said collector electrode to the reference potential point to selectively short out the feedback connection and then allow feedback when the contact is opened, said transformer and said circuit means being constructed so that the frequency of said oscillations is such that a plurality of oscillations is produced each time the timer renders the feedback operative, and means connecting said third winding to the distributor to apply the oscillations thereto.

10. An ignition system for producing from a low voltage electrical supply a high voltage spark discharge at ignition means provided ina combustion chamber for ignition of a combustible mixture therein, said ignition system including in combination, an oscillator having a transistor and a transformer, said transistor having emitter, collector wd base electrodes, said transformer having a saturable core and primary, secondary and feedback windings inductively coupled through said core, potential supply means, circuit means coupling said transistor to said potential supply means, said circuit means having a portion connecting said primary winding in circuit with said emitter and collector electrodes of said transistor, said circuit means connecting said base electrode to said feedback winding to provide feedback for producing oscillations, said oscillations saturating said core so that sharp voltage pulses are induced in said secondary winding, and means for connecting said secondary winding to the ignition means to apply said pulses thereto for causing a spark discharge to produce ignition of the mixture in the combustion chamber.

11. An ignition system for producing a high voltage spark discharge at ignition means for a burner which is operated from a low voltage direct current, and which burner includes a combustion chamber in which a mixture is ignited by the spark discharge, such ignition system including, an oscillator having a transistor and a transformer, said transistor having emitter, collector and base electrodes, said transformer having a saturable core and primary, secondary and feedback windings coupled through said core, circuit means connecting said primary winding in circuit with said emitter and collector electrodes of said transistor, said circuit means connecting said feedback winding to said base electrode to provide feedback through said transistor, means applying direct current potentials to said transistor to produce oscillations therein, said oscillations saturating said core so that sharp voltage pulses are induced in said third winding, and means connecting said secondary winding to the ignition mean-s to apply said pulses thereto to produce ignition of the mixture in the combustion chamber of the burner.

12. An ignition system for producing a high voltage spark discharge at ignition means for a burner which is used in a vehicle having a low voltage electrical system, and which burner includes a combustion chamber in which a combustible mixture is ignited by the sparkdischarge, such ignition system including in combination, an oscillator having a transistor and a transformer, said transistor having base, emitter, and collector-electrodes, said transformer having a saturable core and primary, secondary and feedback windings inductively coupled through said core, circuit means connecting said collector electrode of said transistor to said primary winding, an energizing circuit for connection to the low voltage electrical system and connected to said emitter electrode to apply operating potential thereto, said circuit means connecting said feedback winding to said energizing circuit and to said base electrode to provide operating potential and feedback thereto for producing oscillations in said primary winding, so that high voltage pulses are induced in said secondary winding, and means connecting said secondary winding to the ignition means to apply said pulses thereto to produce a spark discharge at the ignition means and cause ignition of the mixture in the combustion chamber of the burner.

References Cited in the file of this patent UNITED STATES PATENTS OTHER REFERENCES Electronics, April 1945, pp. 108 and 109.

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